The objective of the invention is to improve the heat stability, (i.e. the heat resistance) of said workpieces.
It is known to use plastic parts, in particular plastic pistons, in motor vehicle brakes. This has in particular the advantage that due to the poor thermal conductivity by the plastic the heat generated in the brake linings on braking is transmitted to the brake fluid to a reduced extent. Heating of brake fluid is extremely undesirable in braking systems because the bubble formation occurring on heating in the brake fluid can considerably impair the braking effect.
If workpieces of a duroplast are heated to the socalled glass transition temperature this may result, in particular on very rapid heating, in an explosion-like liberation of gases in the plastic with a consequent impairing of the stability of the material, in particular by crack formation or the like.